Telephone system



V. s. THARP TELEPHONE SYSTEM Filed Dec. fr, 1931 P. sheets-sheet 2 April 25? E935.

[Ward I@ d? Wim' E) *Us Patented Apr. 25, 1933 UNiTED STATES PATENT OFFICE VICTOR S. THARP, DECEASED, LATE OF ELMHURST, ILLINOIS, BY BESSIE MARY THARP, ADMINISTRATRIX, OF ELMI-IURST, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO ASSOCIATED ELECTRIC LABORATORIES, INC., OF' CHICAGO, ILLINOIS, A CORPO- RATION OF DELAWARE TELEPHONE SYSTEM Application filed December '7, 1931. Serial No. 579,416.

The present invention relates in general to telephone systems and more particularly to automatic telephone systems employing the well-known Strowger or other similar switches to establish the telephone connections. The main object of the invention is the improvements of such switches to secure more certain and reliable operation.

A Strowger switch usually employs a socalled release relay which is operated responsive to the operation of the line or impulsing relay when the switch is seized, and which remains operated during the time that the switch is in use to maintain the circuit to the release magnet open. This relay is made slow-torelease by a copper slug on the heel end of the core, or in any other suitable manner, so that it will not release when the line or impulsing relay releases responsive to impulses. Sonie diliiculty has been experienced in properly adjusting the tension of the springs on this release relay so that it'will fall back properly when its circuit is perj inanently opened by the line relay and yet be suiiiciently slow to hold up during momentary interruption of its circuit during impulsing. Furthermore, it is often desirable to provide a large number of springs on this relay to control various holding and locking circuit-s. In the past, the number of springs which could be placed on the release relay has been limited due to the critical adjustment of the relay. y

A particular feature of the present invention, therefore7 is the provision of means for insuring the continued operation of the release relay during iinpulsing. Accordingv to the invention, this is accomplished by momentarily completing an auxiliary circuit for the release relay during the time its circuit is opened by the release of the line or impulsing relay responsive to received impulses.

The above' and other features of the invention may be best understood from a perusal of the following specification when read in connection with the accompanying drawings, comprising Figs. 1 to 3, inclusive, in which Fig. 1 is a front view of a portion of a vStrowger vertical and rotary switch showing the mechanical arrangementl of the double dog and the springs operated thereby, and

Figs. 2 and 3 show by means of the usual circuit diagram the apparatus involved in a telephone connection.

The lineswitch LS indicated in Fig. 2 of the drawings is the well-known rotary lineswitch in which the wipers have no normal position but remain in the position last used. The selector S indicated in Fig. Qinay be a so-called battery-searching selector switch having a directive vert-ical movementand an automatic rotary movement. A suitable selector switch is disclosed in the co-pendiiig Tharp application, Serial No. 510,680, led January 28, 1931. The connector C shown in detail in Fig. 3 of the drawings is a coderinging party-line connector having access to two hundred party lines through two sets of wipers. This connector is somewhat similar to that disclosed in the above-inentioned Tharp application.

Referring now to Fig. 1 of the drawings, the reference character 1 represents a portion of the fram-e of a two-motion vertical and rotary switch, such as the well known Strowger switch. The shaft 2 which carries the wipers (not shown) is arranged to be stepped vertically by the pawl of the vertical niagnet (not shown) engaging the vertical teeth, such as 3. The pawl ot the rotary magnet, also not shown, steps the shaft and wipers in a rotary direction by engaging the rotary teeth7 such as l. The stationary dog 9 holds the switch in its vertical direction after the shaft has beenstepped off-normal in its rotary direction. The double dog 5 which is pivoted on the vertical pin 8 has a vertical detent .7 which prevents the vertical release of the switch during its vertical movement, and a rotary detent (i which prevents the rotary release of the switch during its ro.

tary movement. Vhen the vertical magnet is energized, its pawl engages one of the teeth 3 and raises the switch shaft one step in its vertical direction. The double dog 5 is rotated around pin 7 when the shaft is raised since the detent 7 rides to the top yof a vertical tooth and then drops to the bottom of the succeeding tooth to hold the switch shaft while the vertical magnet is releasing and disengaging its pawl preparatory to taking another step. Similarly, when the shaft is being rotated responsive to successive energizations ot the rotary magnet, the rotary detent 6 rides to the top ot a rotary tooth and drops to the bottom et the succeeding tooth thereby rotating the double dog around pin 8.

The upper end ot the shaft 2 passes through a bearing 10 and a hole in the angle bracket 11 which is fastened to the switch trame by means of screws 12. On the bracket 11 are mounted the double dog springs comprising a dead spring 16 and contact springs lll and 15, separated by suitable insulators. The spring combination is mounted to the bracket 11 by means or" screws 13.

The dead spring 16 and contact spring 15 are separated by a bushing at their outer ends and these two springs furnish the tension for keeping the double dog detent-s in engagement with the vertical and rotary teeth on the switch shaft. The distance between the contacts on springs 15 and 14 is so adjusted that when the switch is being stepped vertically and the double dog detent 7 rides to the top of a tooth, these contacts are closed. Similarly, when the shaft is being rotated, the detent 6 in riding to the top ot a tooth rotates the double dog 5 suillci-ently so that springs 15 and 16 are operated to the right sutiiciently to make the contact between springs 14 and 15. Thus it is seen that whenever the switch shaft and wipers are being stepped either vertically or horizontally, springs 14 and 15 make contact at each step of the switch. The utility ot this arrangement will be explained hereinafter in connection with the circuit ot connector C shown in Fig. 3 of the drawings. It is to be understood that the arrangement is equally applicable to selector switch, such as indicated as S in Fig. Q ot the drawings, or to any similar switch.

Referring now to the circuit diagram in Figs. 2 and 3 ot the drawings, it will be assumed that the subscriber at substation T desires to establish a telephone connection to the subscri er at substation T2, whose number it will be assumed is 3155. Th-en the receiver is removed at substation T, a loop circuit is closed over conductors 25 and 26, extending to the rotary lineswitch LS over conductors 30 and 31. The rotary lineswitch LS operates in known manner to select an idle trunk extending to a selector, such as S. then an idle selector, such as S, has been seized, the line and release relay of the selector operate and the release relay returns ground over conductor 36 and through wiper 33 ot the rotary lineswitch to hold the lineswitch operated and also to busy the line of substation T in the banks of connectors having access thereto by placing ground on conductor 28. Responsive to the dialling oi the first digit 3, the selector switch S is operated to step the switch wipers opposite th-e third level ot bank contacts, and the switch then automatically rotates to lind an idle trunk in this level. t will be assumed that the connector C available over bank contacts 41, 42, and e3 and trunk conductors t, 15, and lr6 is the connector' which is seized by selector S over wipers 3S, 39, and 40.

Responsive to the extension of the loop circuit over conductors a and i6 to the connector C, line relay 55 of the connector operates in circuit extending from battery, upper winding et relay 55, normally closed springs controlled by armature 52, conductor 14, bank contact 41 and wiper 38 et selector S, conductor 35, the bank contact engaged by wiper 32 and said wiper, conductor 30, line conductor 25, the substation T, line conductor 26, conductor 31, wiper 34 and bank contact, conductor 37, wiper i0 and bank contact L13, conductor 46, normally closed springs controlled by armature 51, lower winding of relay 55, to ground. Belay 55 operates and at armature 56 and its working contact completes an obvious circuit for the release relay GO. Relay GO operates in this circuit and at armature and its resting contact removes battery potential from the test conductor 45 which was necessary to mark the switch idle to the battery searching selectors, such as S, and at the working contact of this armature places ground on conductor 45 to hold the selector S and lineswitch LS operated. At armature 61 and its working contact it places ground on conductor 14.0 to prepare various holding circuits as will be explained later. At armature 62 and its working contact it prepares a circuit for itself through the double dog springs 141 and 15. At armature (33 and its working Contact it prepares the impulsing circuit, and at armature Gt and its resting contact it opens a point in the release circuit ot the switch.

The connector C is a code-ringing partyline connector having access to two-hundred lines over two sets ot wipers. The connector is equipped with a minor switch M which selects the set of wipers to be used and the code to be used in ringing the called line responsive to the first digit dialled into the switch. In the assumed case, this iii-st digit is 1. lhen the subscriber at substation T operates his dial in accordance with the digit 1, line relay 55 releases momentarily responsive to the interruption et the subscribers loop, and at armature 56 and its resting contact completes a circuitl from ground, armature 5G and its resting contact, armature 63 and its working contact, armature 91 and its resting Contact, resting Contact of armature 100 and said armature, winding of series relay 66 to battery, and in multiple therewith through armature 76 and its resting contact, off-normal spring 72 and its resting contact, winding of rotary magnet 112 of minor switch M, to battery. The rotary magnet of the minor switch energizes and advances wipers 116 and 117 to the first bank contacts. Relay 66 operates in multiple with the rotary magnet 112 without effect at this time. When relay 55 again energizes at the end of the impulse, the circuit to series relay 66 and the rotary magnet 112 is broken and the relay and magnet deenergize. n

A diagrammatic `showing of the minor switch has been made to illustrate the manner in which the springs 113 to 115, inclusive, are operated. When the rotary magnet 112 is energized, it operates its pawl 143 which engages one of the teeth on the ratchet wheel 142, thereby rotating the ratchet wheel 142 one step in a clockwise direction. This rotates wipers 116 and 117 onto the first bank contacts. As the ratchet wheel 142 is rotated, the release detent 144 rides to the top of the tooth on the ratchet wheel and in so doing operates the spring 113 into engagement with the dead spring 115. This closes a passing contact through spring 113, spring 115, and spring 114 while all three springs are in engagement. The release detent 144 rides to the top of the tooth and drops to the bottom of the next tooth, maintaining the three springs in engagement with each other until it again drops to the bottom of the next tooth. The spring 114 is adjusted to follow s ring 115 during this movement, but when t e release magnet 111 is energized to attract the release detent 144, the detent is moved entirely away from the ratchet wheel thereby operating springs 113 and 115 a suiiicient distance so that spring 114 does not follow. The contact between springs 114 and 115 is then broken.

From the foregoing it is seen that when the line relay releases to repeat the first impulse to the magnet of the minor switch, it breaks the circuit ot release relay 60 at armature and its werking contact, while at the resting contact of this armature it transmits an impulse to the rotary magnet of the minor switch. The rotary magnet energizes and steps the miner switch one step and during this step the release detent 144 furccd outward the teeth on the ratchet wl sel, thereby bringing springs 113. 114, and 115 into Contact with cac-h other. This completes a circuit from ground at armature 61 of relay 6 and the working Contact of this armature, conductor 140, spring 114, spring 115, spring 113, winding ci' release relay 60 to ba ry. This circuit is closed momentarily during the time that the initial energizing circuit et relay 60 is opened at armature 56Y and its working contact. Thus a momentary impulse of current is sont through the winding of relay 60 to maintain the magnetism in its core and thereby prevent any possibility of the release of this relay during the time that its circuit is opened when the line relay 55 releases to repeat the impulses. f

A short interval aft-er the termination of the first impulse series, which in this case consisted of only one impulse, relay 66 releases and at armature 68 and its resting contact completes a circuit from the grounded conductor 140, first bank contact engaged by wiper 116 and said wiper, armature 68 and its resting contact, oli-normal contact 145, lower winding of ring-cut-ofl relay 73, to battery. Relay 73 energizes after any interval and at armature 75 anc its working contact prepares a locking circuit for itself. At armature 7 6 and its rest-ing contact it opens the impulsing circuit to the rotary magnet oi the minor switch M, and at the working contact of this armature it prepares the impulsing circuit to the vertical magnet of the connector. he operation of armatures 74 and 77 is without eiect at this time.

TWhen the subscriber at substation T operates his dial in accordance with the next digit, which in this case is assumed to be 5, ine relay 55 momentarily releases and reoperates live times, thereby sending five impulses to vertical magnet 70 over the following circuit: from ground, armature 56 and its resting contact, armature l63 and its working contact, armature 91 and its resting contact, resting contact of armature 100 and said armature, winding of series relay 66 to battery, and in multiple therewith over armature 76 and its working' contact, winding of vertical magnet 70 to battery. At the first vertical step off-normal springs 145 open. but at'this time relay 66 is energized and at armature 68 and its working Contact completes the locking circuit for relay 7 3 which extends from grounded conductor 140 in the previously traced circuit over armature 68 and .its working Contact, armature and its working contact, lower winding of relay 7 to battery. Responsive to the five successive energizations of vertical magnet 70, the switch shaft and wipers are stepped vertically to a position opposite the fifth level of bank contacts. y At each step of the switch, the vertical detent 701? the double dog 5 (shown in Fig. 1) rides to the top of a vertical tooth 'thereby operating springs 15 and 16 so that springs 14 and 15 make contact and complete a momentary holdi'ngcircuit for rthe release relay 60 extending from ground at the working Contact of armature and said armature, springs 14 and 15 of the double deg spring combination. winding oi relay 60 to battery. This circuit is effective during the time that the initial energizing circuitl of relay 60 is opened while the line relay 55 is repeating the impulses to the CII vertical magnet. This prevents any possibility oi' the deenergization oic the release relay When its circuit is intermittently opened by the line relay responsive to received impaises.

A short time after the termination of the vertical impulses, .series relay 6G releases and at armature 68 and its Working contact opens the locking circuit of relay 'T2-l. The initial energizing circuit o1E relay 73 over the baci; contact of armature G8 is now open at olfnormal springs 1415. After an interval relay .73 releases and at armature and its Working contact opens a point in its own locking circuit, at armature 7G and its Working contact it opens the impulsing circuit oi the vertical magnet 70, and at the resting contact of this armature it prepares the impulsinv circuit to the rotary magnet 71. Gif-normal spring 72 opened its resting contact at the lirst vertical step orl the switch and is no-W'in engagement with its Working contact.

lilhen line relay 55 is intermittently deenergized in accordance with the digit 5 next dialled by the subscriber at substation T, live impulses are transmitted to the rotary magnet 'T1 over the following circuit: from ground, armature 5G and its resting contact, armature G3 and its working contact, armature 91 and its resting contact, resting con tact of armature 100 and said armature, 'inding ot relay 56 to battery, and in multiple therewith over armature 76 and its resting contact, oli-normal spring 72 and its Working contact, Winding or' rotary magnet 71 to battery. The rotar Y magnet 71 is thereby momentarily energized liye times and steps the shaft and Wipers in a rotary direction into engagement yith the liith set of bank contacts. At each step of the switch and While the initial energizing circuit of relay (30 is open at armature 5G and its Working contact, the double dog Springs 14 and 15 are operated by the detent G of' double dog 5 riding to 'the top of the rotary teeth and an auxiliary holding circuit is thereby completed for release relay G9 from ground at the Working contact o1" amature 62. This auxiliary holding circuit insures the continued energization oi the release relay during impulsing.

At the end of the rotary series of impulses and before the sloW-torelease series relay GG has had time to deenergize, the called line is tested over the following circuit: test Wiper 119, rest-ing contact of armature 108 and said armature, normally closed springs controlled by armature 97, normally closed springs controlled by armature 89, Working Contact oi" armature 67 and said armature, resistance 9-l. Winding of relay 87 to battery. It will lirst be assumet that one of the subscribers on the party line to Which substation T2 is connected is already engaged in a conversation and that this line is, therefore, busy. In this case there will be ground potential present on test bank contact 125, and this ground potential is extended over test Wiper 119 and the above traced test circuit- Relay S7 is a two-step relay and can operate only in its iirst step through resistance 911. Tn operating in its lirst step, relay 8T closes only armature 90 and its Working contact, thereby preparing a circuit for its Winding independent of resistance 9st. After an interval the slow-to` release series relay G6 dcenergizes and at armature GT and its working contact opens the initial test circuit to relay 87 and at the normally closed springs controlled by armature 6T it completes the circuit through armature 90 and its working contact independent of resistance Sil. 1When this circuit is cornpleted, relay 8T operates in its second step and at armature 91 and its resting contact opens point in the impulsing circuit, at armature 39 and its working contact it loelis itself to the release trunk conductor 45 and at armature 8S and its Working contact it connects the busy-tone lead 92 to the negative trunl; conductor ll through condenser 58. Busy tone from tl e busy-tone machine, shown in the upper portion of the drawings, is new transmitted over the negative conductor to the calling substation to inform the calling subscriber 'that the desired called line is busy. The calling subscriber at substation T thereupon replaces his receiver bringing about the release of the switch train in a manner to be hereinafter described.

It Will nor: be assumed that the party line comprising conductors 192 and 133 accessile over bank contacts 124C, 125, and 126 of the connector switch and over Which access is had to substation T2 is idle when the connector switch C is operated into engagement 'with the banl; contacts. ln this case, there is no ground potential on banl-r contact 125 and relay 87 does not energize in the previously traced testing circuit. lWhen relay 66 releases a short time aiter the termination of the rotary series of impulses, a circuit is coinpleted for the wiper connecting relay 95 in series with the usual cut-oliq relay of the lineswitch Which terminates conductors 13T, 1538, and 139. This circuit extends from battery, through the cut-oli'l relay of the lineswitch, conductor 13S, baril: contact 125, Wiper 119, resting contact of armature 10S and said armature, normally closed springs controlled by armature 9T, normally closed springs controlled by arma-ture 89, normally closed springs controlled by armature 6T, armature 90 and its resting contact, lower Winding of Wiper connecting relay 95, to ground on the release trunlr conductor 45.

Relay 95 energizes in this circuit and at armature 99 and its Working contact locks itself energized to the grounded conductor 140 over its upper Winding. At armature 10() and its resting contact it opens a point in the impulsing circuit, at armature 101 and its working contact it prepares a locking circuit for the ring-cut-off relay 73, at armature 102 and its working contact it prepares a circuit to the pick-up relay 80, at armature 108 and its resting contact it opens a point in the test circuit over which selectors having access to the connector switch C test the release trunk conductor for battery potential, at armature 98 and its working Contact it prepares a locking circuit for wiper-switching relay 106 which does not enter into the connection being described, at armature 97 and its working contact it places ground through armature 108 and its resting contact and wiper 119 on banh contact 125, thereby marking the called lin-e busy to all other connectors having access thereto, and at armatures 96 and 104 and their respective working contacts it completes a ringing circuit to the called line, dependent upon the operation of pick-up relay 80.

The pick-up conductor 108 extends to the code-ringing machine as do the code eonductors 146 to 150, inclusive. The pick-up conductor 105 is grounded by the code-ringing machine between codes so that ringing by any one connector cannot be started except at the beginning of the code. This prevents a part of a code being sent out to the called line as a ringing signal. Then conductor 105 is grounded at the beginning of a ringing code, relay 80 operates and at armature 81 and its working contact locks itself operated to grounded conductor 140. At armature 82 and its working contact it completes the ringing circuit extending in the assumed case from code conductor 146 and the first bank contact engaged by wiper 117 of the minor switch, wiper 117, working contact of armature 82 and said armature, upper winding of ring-cut-ofl:l relay 73, armature 84 and its resting contact, resting contact of armature 74 and said armature, armature 96 and its worlring contact, armature 107 andits resting contact, wiper 118 and bank contact 124, conductor 133 of the called line, through the bells at the party-line substations connected to this conductor of the line, to ground.

When the party-line subscriber hears his code he answers the call by removing his re` ceiver, thereby completing a direct current path through his substation and allowing current to ilow through the upper winding of riiig-cut-off relay 7 3 of the connector. This circuit extends from battery at the code-ringing machine over the above-traced ringing circuit to conductor 133, the direct current path through the substation which has answered the call, conductor 132. bank contact 126 and wiper 120, resting contact of armature 110 and said armature, armature 104 and its Working contact, armature 77 and its resting contact, resting contact of armature ture 101 and its working contact. At ariiia- ,1.

tures 74 and 77 and their respective resting contact it disconnects the ringing and ringcut-otf circuits, and at the working contacts of these armatures it short circuits the condensers 79 and 78 which are provided. to al-. low a portion of the ringing current to leak n bach to the calling line as a ring-bach signal, and completes the circuit for the back-bridge relay over the called subscribers loop. At

armatures 51 and 52, relay 50 reverses the battery connections to the called line for supervisory or metering purposes, at arniature 53 it makes an additional ground connection to the` conductor 140, and at armature 54 it opens a point in the circuit of the release magnet of the switch. The connection from the subscriber at substation T has now been established to the desired subscriber at sub# station T2 on the partydine comprising conductors 132 and 133 and coversation may take place.

At the end of the conversation, when the subscriber at substation T replaces `his receiv er the loop circuit extending to line relay 55 of connector C is opened and this relay, accordingly, releases. At armature 56 and its working contact it opens the circuit of release relay 60.` After an interval relay 60 releases and at armature 61 and its working contact einoves one ground connection from conductor 140, but this conductor is grounded at armature 58 and its working contact as long as the called subscriber maintains his receiver oit the hook. Assuming that the called subscriber has replaced his receiver, relay 60 completes the release circuit of the switch extending from ground at armature 64 and its resting contact, armature 54 and its resting contact, olf-normal springs 57, winding of release magnet 69, to battery. Release magnet 69 operates to bring about the release of the switch and at its armature 151 and resting contact it removes battery from the release trunlr conductor 45 so that the switch cannot be seized by a selector until it has conipletely restored to normal. The release circuit for the minor switch M is also closed from ground at armature 64 and its resting contact, off-normal springs 141 of the minor switch, winding of release magnet 111 to battery. Release magnet 111 operates and disengages the release detent 144 from the teeth of ratchet wheel 142 and allows the minor switch to restore to normal under spring power. The release detent 144 in this case is operated a sufficient distance so that the contact between springs 114 and 115 is opened.

Relays and 95 release when ground is removed from conductor 140 and relay 95 in releasing opens the locking circuit of ringcut-ott relay 73 thereby allowing this relay to release. lVlien the connector switch has com pletely restored to normal, oil-normal con tacts 57 are opened, thereby opening the circuit to the release magnet 69 which deenergizes and again completes the testing circuit to the switch through armature 151 and its resting contact. The release circuit to release magnet 111 of the minor switch M is 10 opened at olf-normal springs 141 when the wipers of the minor switch have been restored to normal.

When ground is removed from release trunk conductor 415 at armature 65 and its working Contact by the release of relay 60 of the connector, the selector switch S which was held operated by this release ground releases in known manner. All the apparatus used in the establishment o't' the connection from substation T to substation T2 on the party line comprising conductors 132 and 133 has now been restored to normal.

The connector switch C shown in Fig. 3 of the drawings is arranged Jfor live-party code ringing. lith the strappings ol' the minor switch banks as shown in the` drawings, the live substations on party line comprising conductors 132 and 133 are arranged with three of the bells at the substation conneeted from the negative line conductor 133 to ground and with the bells at the other two substations connected between the positive line conductor 132 and ground. Codes 1. 3, and 5 are transmitted over conductor 133 to signal the three subscribers whose bells are connected between this conductor and ground, and codes 2 and 4 are transmitted over the positive conductor 132 to signal the remaining two subscribers. On the party line comprising conductors 130 and 131, the bells at three of the substations are connected between the positive line conductor 130 and ground, and the bells at the remaining two substations are connected between the negative line conductor 131 and ground. Codes 1, 3, and 5 are transmitted over the positive conductor 130 to signal the three subscribers whose bells are connected to this side of the line, and codes 2 and 4 are transmitted over 'J0 the negative line conductor 131 to signal the two subscribers whose bells are connected to this side of the line.

In order that the ringing arrangement and that the manner ot selecting the set of wipers to be used in the establishment of the call may be clearly understood. the operation of the connector switch C will be explained on several other dilierent calls. In the connection `inst explained, code No. 1 was trans- 50 mitted over the negative line conductor 133 to signal one ot the subscribers on this line. It will now be assumed that a subscriber on the party line comprising conductors 130 and 131 is being called. In this case the first digit dialled into the connector C will be 2, 4, 6, 8, or 10, depending upon the party on this line which is being called. It will be assumed that this lirst digit is 2, in which ease the desired subscriber is connected between the positive line conductor 130 and ground.

The initiation of the call by the subscriber at substation T and the operation of the lineswitch LS and selector S to extend the connection to a connector switch, such as C, is the same as previously described. lVhen the connector switch C is seized, line relay and release relay operate in the same manner as previously described. Release relay 60 prepares the impulsing circuit at armature 63 and its working contact and at armature 65 and its working Contact connects ground to release trunk conductor 45 to make the switch C busy to other selectors having access thereto. In this case, the first digit dialled to the connector C is 2 and the line relay 55, therefore, momentarily releases twice. At each release, an impulse is transmitted from ground, armature 56 and its resting contact, armature 63 and its working Contact, armature 91 and its resting contact, resting contact of armature 100 and said armature, winding of series relay 66 to battery, and in multiple therewith over armature 76 and its resting contact, oil-normal spring 72 and its resting contact, winding of rotary magnet 112 of the minor switch M to battery. The minor switch M, therefore, takes two steps and moves its wipers 116 and 117 into engagement with their respective second bank contacts. Series relay 66 energiZes during the impulse series.

A short interval after the impulse series has been terminated, relay 66 releases and at armature 68 and its resting contact completes a circuit extending from the grounded conductor 140, lower winding of wiper-switching relay 106, upper winding of ring-reversing relay 83, second bank contact engaged by wiper 116 and said wiper, armature 68 and its resting contact, olf-normal contacts 1415, lower vi ding of relay 73 to battery. Relays 73, 83, and 106 energize in series in this eircuit. Relay 106, in energizing, at armature 109 and its working contact locks itself energized to the release trunk conductor L15 through the normally closed springs controlled by armature 98 of relay 95. At armatures 107, 108, and 110, it transfers the connections from wipers 118, 119, and 120 to the second set of wipers 121, 122, and 123. Re lay 83 at armature 86 and its working contact completes a locking circuit for its lower winding extending from ground on eonductor 110, lower winding et relay 83, working contact of armature 86 and said armature, resistance 93 to battery. At armatures 8l and 85 it reverses the connection of the ringing leads to the line conductors.

At the lirst impulse of the succeeding digit 5, relay 73 locks energized through armature 7 5 and its working contact, and working contact of armature 68 and said armature, as long as the series relay 66 is operated. When this relay releases at the end of the vertical series of impulses, it opens the circuit of relay 73 and allows this relay to release and prepare the circuit to the rotary magnet. The last digit 5 is received and live impulses are transmitted to the rotary magnet of the switch to operate the wipers into engagement with bank contacts 127, 128, and 129 over which access is had to the party line comprising conductors 130 and 131. The operation of the switch for the last two digits is the same as that previously described. Before the series relay 66 releases at the end of the rotary series of impulses, the called party line is tested for busy or idle condition by relay 87 in the same manner as previously described.

Assuming that the line is idle, a circuit is completed for wiper-connecting relay 95 as soon as the slow-to-release series relay 66 releases. Relay 95 operates and at armatures 96 and 104 and their respective working contacts completes the ringing and ring-cut-ofi circuits to the called line. In this case the ringing circuit extends from the battery-connected code-ringing machine, over conductor 146, the second bank Contact engaged by wiper 117 ot the minor switch, wiper 117, working contact of armature 82 and said armature, upper winding of ring-cutoff relay 73, armature 84 and its working contact, resting contact of armature 77 and said armature, working contact of armature 104 and said armature, armature 110 and its working contact, wiper 123 and bank contact 129, conductor 130, through the bells at the substations connected to this line conductor, to ground. Code No. 1 is transmitted over this ringing circuit and operates the bells connected between conductor 130 and ground. The desired subscriber upon hearing his code removes his receiver, thereby completing a direct current path for the upper winding of ring-eut-otf relay 73 which includes the above ringing circuit over conductor 130, the direct current path through the called subscribers substation, conductor 131, bank contact 127 and wiper 121, working contact of armature 107 and said armature, working contact of armature 96 and said armature, armature 74 and its resting contact, working contact of armature 85 and said armature to ground. Relay 73 operates in this circuit and at armatures 74 and 77 cuts off the ringing current, short-cirouits condensers 78 and 79, and completes the circuit to back-bridge relay 50 over the called loop. Relay 73 locks itself energized over armature 7 5 and its working contact to ground at armature 101 and its working contact. The circuit to the desired subscriber on the party line comprising conductors 130 and 131 has now been completed and conversation may take place. At the end of the conversation, the release of the switch train used in the establishment of the connection is effected in the same manner as previously described.

Assuming' now that the calling subscriber at substation T wishes to converse rit-h a sub scriber on the party line comprising concluetors 132 and 133 whose code signal is code No. 2 and whose bells are connected to the positive Lline conductor 132. In this case the first digit dialled to the connector switch C will be 3. Responsive to this digit the minor switch M rotates its wipers into engagement with the third bank contacts and the following circuit is completed when series relay 66 releases at the end of' the first digit: from grounded conductor 140, lower winding of relay 83, third bank contact engaged by wiper 116 of minor switch M, wiper 116, armature 68 and its resting Contact, off-normal springs 145, lower winding of relay 73, to battery. Relays 73 and 83 energize in series in this circuit and relay 83 locks itself energized to grounded conductor 140 over its lower winding at armature 86 and its working contact. At armatures 84 and 85 it reverses the ringing connections to the line conductors. In this case the wiper switching relay 106 is not energized and the normally connected set of wipers 118, 119, and 120 is used.

Assuming that the caller line is idle, relay 95 operates in the manner previously described and completes the ringing circuit, after the operation of pick-up relay 80, from battery at the code-ringing machine, conductor 147, third bank contact engaged by wiper 117 an d said wiper, working contact of armature k82 and said armature, upper winding of ring-cutoff relay 7 3, armature 84 and its working contact, resting contact of armature 77 and said armature, working contact of armature 104 and said armature, armature 110 and its resting Contact, wiper 120 and bank Contact 126, over the positive line conductor 132, through the bells ol' the substations connected to this side of the line to ground. Then the subscriber hearing code No. 2 picks up his receiver, ring-cut-otl relay 73 is operated in the above traced ringing circuit including line conductor 132 and through the direct current bridge at the called substation, conductor 133, bank contact 124 and wiper 118, resting contact of armature 107 and said armature, working contact of armature 96 and said armature, armature 74 and its resting contact, werking contact of armature 85 and said armature to ground. Relay 73, at armatures 74 and 77, cuts olf the ringing current, short-circuits the ring-back condenser-s 78 and 79, and completes the circuit ot relay 50 over the called loop. The connection to the desired called subscriber has now been established and the conversation may proceed. The release of the connection is brought about in the same manner as previously described.

Assuming nou' that the subscriber at suostation T Wishes to converse vfith a subscriber on the party lin v and 131 Whose bells z. f connected to the negative s e vfho has been assigned code So. 2. the lirst digit dialled lo the connector in, and the minor Yitch nl ture (5o l Y springs 115, lower Winding or rmg-cut-oll' relay t .v Relays 73 and 100 optratc in seres in 'this circuit and relL 10b at armatures 10ic 108, ind 110 disconnects the normaily-connected of Wipers and connects up the Wipers 121, 122, and Relay 1 i itself energized over its upper vrinding at armature 109 and its Working Contact to release trani: ce D nductor '-15. clay T3 rcleases at the termination oit the second series or impulses to transfer the circuit to the rotary magnet oi the switch as previously described, and the remaining digit 5 dialled to operate the connector into engagement with baul; contacts 127. 12S, and 129.

Assuming th the called line is idle, Wiperconnecting relay operates in the manner previously described and locks itself energized to grounded conductor 110. At armatures 9G and 101 it completes the ringing circuit which in this case extends from battery through the code-ringing machine, over conductor 1d?, fourth bank contact engaged by Wiper 117 and said Wiper, working contact of armature 32 and said armature, upper Winding of ring-cut-oi' relay 73, armature 8st and its resting contact, resting contact of armature 71 and said armature, armature 96 and its Working contact, armature 10T and its Working contact, Wiper 121 and bank contact 12?, conductor 131, and to ground through the bells of the substations connected to the line conductor 131. Wlhen the desired party hears his code, which in this case is code No. 2, he removes his receiver from the hook thereby completing the circuit for ring-cut-oii3 relay 73 Ywhich includes the above ringing circuit and extends through the direct current bridge at the called subscribers substation, conductor 130, bank contact 129 and Wiper 123, Working contactof armature and said armature, armature 10% and its Working contact, armature 77 and its resting contact, resting Contact of armature 85 and said armature to gound. Ring-cut-otl relay 73 energizes in this circuit and locks itself to ground at armature 101 of the Wiper-connecting relay 95. At armatures 74 and 77 it disconnects the ringing circuit, short-circuits the ring-back condensers 78 and 79, and completes the circuit for relay 50 over the called loop. The connection has now been completed to the desired called subscriber and conversation may proceed. Release takes place in the same manner as previously described.

It will be seen from an inspection of the multiplying of bank contacts engaged by Wiper 116 of minor switch M that there are four control conductors connected to the lirst four bank contacts and that these conductors are multiplied to the remaining bank contacts. Thus there are four possible Ways in which the reversing relay 83 and the wiper-switching relay 106 may be operated. 'Vhen the digits 1, 5, and 9 are dialled to the minor switch, neither relay 83 nor relay 10G is operated and codes 1, 3, and 5, respectively, are transmitted over the negative line conductor 133. In case the digit 3 or 'i' is dialled, relay 83 is operated and codes 2 and 1, respectively, are transmitted over the positive line conductor 132. This takes care of the tive subscribers on the party line comprising conductors 132 and 133. Similarly, if the digit 2, 6, or 10 is dialled, both relays S3 and 106 are operated and codes 1, 3, and 5, respectively, are transmitted over the positive line conductor 130. Tn case the digit l or S is dialled, relay 106 alone is operated and the codes 2 and el., respectively, are transmitted over the negative line conductor 131. This takes care of the live subscribers on the party line comprising conductors and 131.

From the foregoing explanation of the operation ot the connector' switch C, it apparent that arrangements have been made to momentarily complete auxiliary holding circuits for the release relay of the switch during the intervals when its initial energizing circuit is opened by the release of the impulsing relay responsive to received impulses. This insures the continued operation of the release relay and allows a greater number of springs to be placed on this relay. Also it eliminates the critical adjustment of the spring tension, since sutiicient tension may now be placed in the springs to insure proper release of the relay when its circuit is permanently opened and still insure continued operation of the relay during impulsing'.

that is claimed is:

1. In an automatic switch, a lino relay and a release relay, a circuit for said release relay closed when said line relay operates responsive to the seizure of said switch, means controlled b v said line relay responsive to received digit impulses for operating said switch, and means responsive to the operation of said switch for completing an auX- iliary holding circuit for said release relay during the intervals when said first circuit is opened by the release of said line relay responsive to received impulses.

2. In an automatic switch, a line relay and a release relay, a circuit for said release relay closed when said line relay operates responsive to the seizure of said switch, means controlled by said line relay for operating said switch responsive to received digit impulses, a release circuit for said switch controlled by said release relay, an auxiliary holding circuit for said release relay, and means responsive to the operation of said switch for momentarily closing said holding circuit each time said first circuit is opened due to the release of said line relay responsive to received impulses to prevent the release of said release relay and the closing of said release circuit during impulsing.

3. In an automatic switch, a line relay and a release relay, a circuit for said release relay closed when said line relay operates responsive to the seizure of said switch, means controlled by said line relay for operating said switch step by step responsive to receive-d digit impulses, an auxiliary circuit for said release relay, and means operated by said switch during each step for completing said auxiliary circuit.

4. In a two-motion automatic switch, a line relay and a release relay, a circuit for said release relay closed when said line relay is operated, means for releasing said line relay in accordance with digit impulses, two operating magnets for operating said switch in its two movements, respectively, under control of said line relay, an auxiliary circuit for said release relay, and means mechanically operated by said switch each time one of said magnets is energized for completing said auxiliary circuit.

5. In an automatic switch, a line relay and a release relay, a circuit for said release relay closed when said line relay is operated, means for releasing said line relay in accordance with digit impulses, thereby intermittently opening the circuit to said release relay, means controlled by said line relay for operating said switch step by step, an auxiliary holding circuit for said release relay including a pair of contact springs, and mechanical means for operating said springs to close said auxiliary holding circuit each time said switch is operated one step.

6. In an automatic switch, a rotatable` shaft, means for rotating said shaft step by step, a detent for holding said shaft during said operation, a release relay for controlling said switch, and means controlled by said detent for completing a momentary circuit for said release relay each time said shaft is advanced one step.k f

7. In an automatic switch, a vertically movable shaft, means for operating said shaft step by step in its vertical movement, a detent for preventing the release of said shaft during said operation, a release relay for controlling said switch, and means controlled by said detent for completing a momentary circuit for said release relay each time said shaft is advanced one step.

8. In an automatic switch, a. shaft, means for operating said shaft vertically, means for rotating said shaft, a double dog for preventing the vertical and rotary release of said shaft, a relay for controlling the release of said switch, and means controlled by said double dog for completing a momentary holding circuit for said relay each time said shaft is operated in either of its movements.

9. In an automatic switch, two operating magnets each having a pawl, a shaft having vertical and rotary teeth vengaged by said pawls, respectively, to operate said switch in its two movements, a double dog having two detents engaging said vertical and rotary teeth, respectively, a line relay and a release relay, a circuit for said release relay closed when said line relay is operated, means fork releasing said line relay in accordance with digit impulses to control said operating magnets, said circuit being opened each time said line relay releases, an auxiliary circuit for said release relay, and means operated by the double dog when said switch is stepped in n t' either of its movements for closing said aux- 

